Electric system and method



July 23, 1957 K. s. LION ELECTRIC SYSTEM AND METHOD 2 Sheets-Sheet 1 Filed Dec. '7, 1955 Fig. 3.

Inventor Kurt 6. L ion y m} Afforneys July 23, 1957 K. S. LION ELECTRIC SYSTEM AND METHOD Filed Dec. 7, 1955 2 Sheets-Sheet 2 OUTPUT VOLTAGE (VOLTS) CHANGE I/V/MPEDANQE IO a/F lnve ntor Kurt .5. Lion Afforneys United States Patent ELECTRIC SYSTEM AND METHOD Kurt S.-Lion, Belmont, Mass. Application December 7, 1955, Serial No. 551,539 17 Claims. (Cl. 321-38) The present invention relates to electric systems and methods and, more particularly, to electric systems that are adapted to transduce mechanical motions or other physical changes into electrical energy.

In United States Letters Patent Nos. 2,696,566 and 2,696,584, issued December 7, 1954, to Kurt S. Lion and John W. Sheetz, 3rd, there are described electric circuits in which either a mechanical displacement or a change of impedance can be transformed into electric output signals by means of gaseous-discharge tubes or other ionizable media containing two or more electrodes. In accordance with two embodiments of the inventions therein disclosed, a discharge is maintained between an outside auxiliary electrode, which may be either fixed or movable relative to the tube or medium, andtwo inside electrodes. In a further embodiment, the discharge is maintained between two auxiliary outside electrodes overlapping the two inside electrodes. Experience has shown that while these systems work very satisfactorily in practice, under some circumstances of operation, the internal electrodes within the gaseous-discharge tube or other ionizable medium sputter electrode material. The sputtered electrode material, such as metal, is deposited on the Walls of the tube and effects changes in the electric field distribution set up within the tube, thus upsetting the calibration of the same. If the metallic deposit on the glass wall of a gaseous-discharge tube, for example, becomes very heavy, a point may be reached where the discharge ceases to exist, and the effective lifetime of the tube becomes rather limited. As is well known, moreover, the deposit of metal upon the glass wall has an effect similar to a getter, so that during the useful life of the tube, the gas pressure is gradually continuously reduced, correspondingly changing the tube characteristics and giving rise to the requirement for frequent recalibration. Such phenomena are, in some applications, quite disturbing and prevent the use of the gaseous-discharge tubes or other media for a number of applications where stability and long-time operation are required.

An objectof the present invention, accordingly, is to provide a new and improved electric system and method of this character that shall not be subject to such disadvantages and that, to the contrary, give rise to very stable operating conditions and greatly increased operating lifetime.

A further object is to provide a transducer that, because of the above properties, can be used in a multiplicity of applications additional to those to which the prior-art transducers may be put.

An additional object is to provide a new and improved gaseous-discharge transducer tube that is substantially less sensitive to variations in production methods, thereby to reduce substantially the production cost of transducers.

Further advantages of this invention will become evident from the explanation hereinafter given, and will be more particularly pointed out in the appended claims.

2,800,622 Patented July 23, 1957 The invention will now be explained in connection with the accompanying drawing,

Fig. 1 of which is a schematic diagram of a gaseousdischarge tube and circuit operated in accordance with the present invention;

Figs. 2 to 5 are similar diagrams of modifications; and

Fig. 6 is a graph illustrating operating characteristics.

In summary, the invention, from its broadest aspect, resides in confining the ionization produced in an ionizable medium, such as a gas-filled tube, to a region of the tube adjacent, but external, to the region containing a pair of internal principal electrodes. The principal electrodes are thus disposed in a space outside of the plasma of the discharge or ionization in the tube. The term plasma is intended to connote not only the positive column of the discharge or ionized region, but also any other part of the discharge or ionized region which contains a substantial concentration of positive or negative carriers. Preferred details are hereinafter explained.

In Fig. 1, a gaseous-discharge tube, as of glass, is illustrated at 1, containing a gas under reduced pressure, as described in the afore-mentioned patents. The tube is shown of preferred, though not essential, longitudinal shape, containing two preferably longitudinal substantially parallel internal principal electrodes 3 and 5 that are connected to output terminals 2 and 4 between which any desired output circuit maybe connected. External to the tube 1 and located adjacent the inner or left-hand ends of the internal electrodes 3 and 5, there are disposed two auxiliary electrodes 6 and 7, spaced from the tube 1 by small air spaces 8 and 9. The auxiliary electrodes 6 and 7 are connected to a source of ionizing potential such as an alternating-current voltage source or oscillator 10 of sufficient voltage magnitude and frequency to initiate and maintain an electrodeless gaseous-discharge plasma or ionization of the glow-discharge type in the left-hand or shaded region of the tube. It is important, in accordance with the present invention, that the discharge or ionization does not substantially enter the righthand region of the tube 1 in which the electrodes 3 and 5 are disposed. Through adjusting the physical dimensions of the auxiliary electrodes 6 and 7 so that they do not, as in prior-art tubes, overlap the electrodes 3 and 5 or any portion thereof, and through utilization of appropriate ionizing voltage from the source 10, preferably of radio frequency to insure sharp confining of the ionized region of the gas in the tube 1, the ionized region remains substantially localized to the left of the line A-A. The circuit of Fig. 1 operates similarly to the circuits shown in, for example, Fig. 9 of. the said Letters Patent No. 2,696,566 and Fig. 3 of the said Letters Patent No. 2,696,584, producing an output voltage at 2, 4 that may be termed a direct-current voltage, as distinguished from the character of the ionizing voltage from the source It), without the necessity for a source of energy in the output circuit. The disposition of the auxiliary electrodes 6 and 7 at the left-hand region of the tube 1, adjacent but to the left of the inner ends of the principal electrodes 3 and 5, however, has been found efiectively to prevent the electrodes 3 and 5 from sputtering. This result is attained, moreover, Without reducing the efiiciency of the transducer tube 1, assuring long-time stability of operation and greatly extended tube life.

The arrangement of Fig. 1, as described in the said Letters Patent, is suitable for the transformation into electrical signals of any relative movement between the tube 1 and the auxiliary electrodes 6 and 7, thereby correspondingly varying the potential gradients within the left-hand region of the tube 1 and the resulting ionization distribution therein. This gives rise to corresponding variations in the output voltage at 2, 4, the magnitude and polarity of which are functions of the extent and direction of relative movements of the tube 1 and electrodes 6 and 7, as explained in the said Letters Patent.

In the modification of Fig. 2, the auxiliary electrodes 6 and 7 are disposed adjacent the tube envelope and a variable impedance element, such as a capacitor 11, which may becontrolled by any desired physical or other force or movement, is connected between the electrodes 3 and 6 to vary the alternating-current potential upon the electrode 6 relative to that upon the electrode 7, correspondingly to vary the ionization distribution in the left-hand region of the tube 1. The magnitude and polarity of the output voltage signal are functions of the magnitude of the capacitor 11 and vary, also, with the grounding conditions of the oscillator or source and/ or of the output terminals 2 and 4. So far as the arrangement of the external auxiliary electrodes is concerned, it is useful to pose them just slightly beyond the principal electrodes, as before explained. Positioning further away from the external electrodes reduces the sensitivity of the transducer and increases its output impedance, but it also increases the useful life of the transducer tube. The designer has, therefore, the possibility of selecting a more sensitive mode of operation with inherently shorter lifetime, or vice versa. It is considered preferable to employ external auxiliary electrodes 6 and 7 cylindrically shaped to surround about one-third of the outside periphery of the glass tube. Two of these electrodes can be held together by means of an insulating ring, not shown, and pressed against the glass wall. By slight rotating and longitudinal shifting of this electrode arrangement, it is possible to adjust the zero output from the terminals 2 and 4. The auxiliary electrodes 6 and 7, however, may also consist of single wires, or they may be painted or sprayed with conductive paint on the glass wall of the tube.

Instead of using just one capacitor or other impedance element to produce an output signal at the output terminals 2 and 4, two or more capacitors may also be used, as shown in Fig. 3. This circuit is identical with that shown in Fig. 2 except that a second variable capacitor 12 is connected from the electrode 6 to the electrode 5. The output signal at 2, 4 will now depend upon the magnitude of the capacitors 11 and 12 and, as before, also upon the grounding condition of the oscillator 10.

While the auxiliary electrodes 6 and 7 have been shown disposed in a plane parallel to that formed by the electrodes 3 and 5, they may be disposed at an angle thereto, as illustrated, for example, in Fig. 4. The internal auxiliary electrodes 6 and 7 of Fig. 4 are oriented so that the direction of the electric field between them is at substantially right angles with respect to the plane formed by the electrodes 3 and 5. A discharge is produced between the electrodes 6 and 7 in the left-hand region of the tube 1 when a sufiiciently high voltage derived from the source 10 is applied thereto. The ionization plasma is confined to the left-hand region of the tube to the left of the inner ends of the principal electrodes 3 and 5. For purposes of illustration, four variable-impedance capacitors 15, 16, 17 and 18 are shown, the capacitors and 16 being connected in the same manner as the capacitors 12 and 11 of Fig. 3, and the capacitors 17 and 18 being connected between the electrode 7 and the electrodes 5 and 3, respectively. The direct-current voltage developed between the output terminals 2 and 4 is a function of the magnitude of the capacitors 15, 16, 17 and 18 and may be made to vary in accordance with a signal or a displacement operating to change the magnitude of one or all of these capacitors. One or several of these capacitors, of course, as explained in connection with the other embodiments of the invention, may be omitted in some applications for which this transducer is to be used. The natural or stray capacitance between one principal electrode and one or the other auxiliary electrode may replace a physical capacitor, also. In Fig. 4-, for instance,

the capacitor 17 may be replaced by the stray capacitance between the electrodes 5 and 7, and capacitance 18 may be replaced by the stray capacitance between the electrodes 3 and 7. The capacitors may all or in part be mechanically linked so that, for example, a simultaneous increase of the capacitances 15 and 18 and a simultaneous decrease of the capacitors 16 and 17 may produce increased impedance changes. On the other hand, balancing systems or servo-systems may be used by having one mechanical or electrical system controlling one capacitor or one set of capacitors, and another system controlling another set, while an output circuit connected between the terminals 2 and 4 gives information about the equality or inequality of the signals acting upon the capacitors.

A simplified system which, in principle, is similar to that shown in Fig. 4 is illustrated in Fig. 5. The internal electrodes 3 and 5 are connected through a differential capacitor 19 to one side of the voltage supply source 10, preferably the grounded side G. Any variation of the position of the middle electrode 20 of the capacitor 19 increases the capacitance of one internal electrode to ground, and decreases the capacitance of the other electrode to ground. This system has proven very stable and has a lifetime far in excess of 1000 hours. The character istic, i. e. the output voltage vs. the capacitance variation AC of such a circuit is plotted in Fig. 6; output voltage being indicated along the ordinate, varying from +50 to ---50 volts, and capacitance change AC being indicated along the abscissa, ranging from 10 to +10 micromicro farads. It is there shown that the output signal is a substantially linear function of the capacitance variation over a considerable range, and deviates from linearity only at extremely large changes of capacitance.

While the invenion has been described in connection with gaseous media, other types of ionizable media such as ionizable solid media may also be employed. Further modifications will also occur to those skilled in the art and all such are considered to fall within the spirit and scope of the invention as defined in the appended claims.

What is claimed is:

l. A method of operating an ionizable medium provided at a predetermined region thereof with two electrodes, that comprises, ionizing only a further region of the ionizable medium external to the predetermined region while maintaining the predetermined region substantially unionized, and extracting electric energy from the electrodes.

2. A method of operating an ionizable gaseous medium provided at a predetermined region thereof with two electrodes, that comprises, ionizing only a further region of the gaseous ionizable medium adjacent to the predetermined region while maintaining the predetermined region substantially unionized, and extracting electric energy from the electrodes.

3. An electric system having, in combination, an ionizable medium provided at a predetermined region thereof with two electrodes, output terminals connected to the electrodes, and means associated with a further region of the ionizable medium external to the predetermined region for ionizing the further region while maintaining the predetermined region substantially unionized.

4. An electric system having, in combination, an ionizable medium provided at a predetermined region thereof with two electrodes, an output circuit connected between the electrodes, and means associated with a further region of the ionizable medium external to the predetermined region for ionizing the further region while maintaining the predetermined region substantially unionized.

5. An electric system having, in combination, an ionizable medium provided at a predetermined region thereof with two electrodes, an output circuit connected between the electrodes, and alternating-current means associated with a further region of the ionizable medium external to the predetermined region for ionizing the further region while maintaining the predetermined region substantially unionized.

6. An electric system having, in combination, an ionizable gaseous medium provided at a predetermined region thereof with two electrodes, an output circuit connected between the electrodes, and means associated with a further region of the ionizable gaseous medium external to the predetermined region for ionizing the further region while maintaining the predetermined region substantially unionized.

7. An electric system having, in combination, an ionizable gaseous medium provided at a predetermined region thereof with two electrodes, an output circuit connected between the electrodes, and alternating-current means associated with a further region of the ionizable gaseous medium external to the predetermined region for ionizing the further region while maintaining the predetermined region substantially unionized.

8. An electric system having, in combination, an ionizable medium provided at a predetermined region thereof with two electrodes, means associated with a further region of the ionizable medium external to the predetermined region for ionizing the further region while maintaining the predetermined region substantially unionized, and an output circuit connected between the electrodes to receive voltage from the electrodes without the aid of a source of energy in the output circuit.

9. An electric system having, in combination, an ionizable gaseous medium provided at a predetermined region thereof with two electrodes, means associated with a further region of the ionizable gaseous medium external to the predetermined region for ionizing the further region while maintaining the predetermined region substantially unionized, and an output circuit connected between the electrodes to receive voltage from the electrodes without the aid of a source of energy in the output circuit.

10. An electric system having, in combination, an ionizable medium provided at a predetermined region thereof with two electrodes, alternating-current means associated with a further region of the ionizable medium external to the predetermined region for ionizing the further region while maintaining the predetermined region substantially unionized, and an output circuit connected between the electrodes to receive the resulting direct-current voltage from the electrodes without the aid of a source of energy in the output circuit.

11. An electric system having, in combination, an ionizable medium provided at a predetermined region thereof with two electrodes, an output circuit connected between the electrodes, means associated with a further region of the ionizable medium external to the predetermined region for ionizing the further region while maintaining the predetermined region substantially unionized, and means for varying the ionization distribution in the said further region to produce corresponding voltage variations in the output circuit.

12. An electric system having, in combination, an ionizable medium provided at a predetermined region thereof with two electrodes, means associated with a further region of the ionizable medium external to the predetermined region for ionizing the further region while maintaining the predetermined region substantially unionized, an output circuit connected between the electrodes to receive voltage from the electrodes without the aid of a source of energy in the output circuit, and means for varying the ionization distribution in the said further region to produce corresponding voltage variations in the output circuit.

13. An electric system having, in combination, an ionizable gaseous medium provided at a predetermined region thereof with two electrodes, alternating-current means associated with a further region of the ionizable gaseous medium external to but adjacent the predetermined region for ionizing the gas in the further region while maintaining the gas in the predetermined region substantially unionized, an output circuit connected between the electrodes to receive voltage from the electrodes without the aid of a source of energy in the output circuit, and means for varying the ionization distribution in the said further region to produce corresponding voltage variations in the output circuit.

14. An electric system as claimed in claim 13 and in which the alternating-current means for ionizing the gas in the said further region comprises electrode means spaced adjacent the said further region, the electrode means being relatively movable with respect to the medium to vary the ionization distribution in the said further region.

15. An electric system as claimed in claim 13 and in which the alternating-current means for ionizing the gas in the said further region comprises electrode means spaced adjacent the said further region, and the ionization-distribution varying means comprises means for varying the alternatingcurrent potential upon the electrode means.

16. An electric system as claimed in claim 15 and in which the alternating-current-potential varying means comprises one or more variable impedance elements con nected between the electrode means and one or both of the said two electrodes.

17. An electric system as claimed in claim 15 and in which the alternating-current-potential varying means is controlled in accordance with mechanical motions.

References Cited in the file of this patent UNITED STATES PATENTS 2,696,566 Lion et al. Dec. 7, 1954 2,696,584 Lion et al Dec. 7, 1954 

